package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.constant.RedisConstant;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

/**
 * @author 刘宇
 */
@Slf4j
@Component
public class CacheClient {

    private final StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }

    //将任意java对象序列化为json并存储在String类型的key中,并且可以设置TTL过期时间
    public void set(String key, Object value, Long time, TimeUnit unit){
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value), time, unit);
    }

    //将任意java对象序列化为json并存储在String类型的key中,并且可以设置逻辑过期时间,用于处理缓存击穿问题
    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit){
        //设置逻辑过期
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        //写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }

    //根据指定的key查询缓存,并反序列化为指定类型 利用缓存空值的方式解决缓存穿透问题
    public <R,ID>R queryWithPassThrough(String keyPrefix, ID id, Class<R>type, Function<ID,R> dbFallBack,Long time, TimeUnit unit){
        //1.从Redis查询商铺缓存
        String key = keyPrefix+id;
        String Json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isNotBlank(Json)) {
            //3.存在 直接返回
            return JSONUtil.toBean(Json, type);
        }
        //判断命中的是否是空值
        if(Json!=null){
            return null;
        }
         R r = dbFallBack.apply(id);
        //5.不存在返回错误 将空值写入redis
        if(r==null){
            stringRedisTemplate.opsForValue().set(key,"",RedisConstant.CACHE_NULL_TTL,TimeUnit.MINUTES);
            return null;
        }
        this.set(key,r,time,unit);
        return r;
    }
    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);
    //根据指定的key查询缓存,并且反序列化为指定类型 需要利用逻辑过期解决缓存击穿问题
    public <R,ID>R queryWithLogicalExpire(String keyPrefix,ID id,Class<R> type,Function<ID,R>dbFallBack,Long time, TimeUnit unit){
        //1.从Redis查询商铺缓存
        String key = keyPrefix+id;
        String Json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isBlank(Json)) {
            //3.缓存不存在 直接返回
            return null;
        }
        //4.命中 需要将json反序列化为对象
        RedisData redisData = JSONUtil.toBean(Json, RedisData.class);
        R r = JSONUtil.toBean((JSONObject) redisData.getData(),type);
        LocalDateTime expireTime = redisData.getExpireTime();
        //5.判断缓存是否过期
        if(expireTime.isAfter(LocalDateTime.now())){
            //5.1未过期 返回店铺信息
            return r;
        }
        //5.2已过期 需要缓存重建
        //6 缓存重建
        //6.1 获取互斥锁
        String lockKey = RedisConstant.LOCK_SHOP_KEY+id;
        //6.2判断是否获取锁成功
        boolean isLock = tryLock(lockKey);
        if(isLock){
            // 6.3 成功 开启独立线程 实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(()->{
                try {
                    //查询数据库
                    R r1 = dbFallBack.apply(id);
                    //写入redis
                    this.setWithLogicalExpire(key,r,time,unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    //释放锁
                    unlock(lockKey);
                }
            });
        }
        //6.4返回过期的商铺信息
        return r;
    }
    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }
    private void unlock(String key){
        stringRedisTemplate.delete(key);
    }
}
